This invention relates generally to wafer demount apparatus and more specifically to wafer demount apparatus having a bridge to protect demounted articles from damage.
Polishing an article to produce a surface which is highly reflective and damage free has application in many fields. A particularly good finish is required when processing an article such as a wafer of semiconductor material in preparation for printing circuits on the wafer by an electron beam-lithographic or photolithographic process. In one well known process for semiconductor wafers, multiple wafers are wax mounted onto a polishing block. The polishing block is placed face down onto a polishing pad so that polish faces of the wafers engage the polish pad. The pad and the polishing block are rotated as a large normal force is applied to the polishing block forcing it down into engagement with the pad. A polishing slurry, typically including chemical polishing agents and abrasive particles, is applied to the pad. Multiple polishing sequences may be carried out to reach the desired final finish of the wafers.
Once polishing is complete the wafers must be removed from the polishing block and inspected for faults. Presently, the polishing blocks are transported, face up, to a demount station where a wedge-shaped prying tool is activated to break the wax bond and detach the wafer from the polishing block. A conveyor is disposed adjacent to the polishing block at the demount station. The prying tool pushes the wafer after it is released from the polishing block onto the conveyor for transport to the inspection station.
It has been found that the wafers fly upward a short distance off of the polishing block and away from the prying tool upon their release from the wax. Thus, the wafer is not controlled for a brief period of time. There is a gap between the edge of the polishing block and the conveyor which is substantially smaller than the diameter of the wafer. Frequently, a leading edge of the wafer flies into the gap so that when the wafer falls back down against the polishing block, the back side of the wafer hits the edge of the block, leaving a mark on the back side of the wafer. It was also possible for the leading edge of the wafer to strike a pulley of the conveyor, causing damage.